1. Field of the Invention
The present invention generally relates to an apparatus for manufacturing a semiconductor device. More particularly, the present invention relates to a turbo pump used to pump air or reaction gas from a reaction chamber in which a semiconductor manufacturing process takes place.
2. Description of the Related Art
Semiconductor devices are manufactured using various apparatuses to perform several different types of processes on a wafer. Generally, the apparatuses used to manufacture semiconductor devices include an ion implantation apparatus that implants impurity ions into a semiconductor wafer, a deposition apparatus that forms a thin film on the semiconductor wafer, and an etching apparatus that etches the thin film. The deposition and the etching apparatuses have closed reaction chambers in order to protect the semiconductor wafer from contaminants in the ambient surrounding the chambers. Also, air is continuously pumped into the process chambers to maintain a high vacuum state or a low vacuum state during a manufacturing process.
FIG. 1 is a schematic cross-sectional view of a conventional semiconductor device manufacturing apparatus. The apparatus generally includes a reaction chamber 10, a main pump 20, an auxiliary pump 50, a roughing valve 80, a foreline valve 90, and a scrubber 70. As mentioned above, a deposition or etching process is carried out in the reaction chamber 10. The first pipe 30 is connected to main pump 20. The second pipe 40 is connected to reaction chamber 10. The roughing valve 80 and foreline valve 90 are disposed in-line with the second pipe 40 and the first pipe 30, respectively, to open and close the pipes. Main pump 20 is used to produce a high level of vacuum within the reaction chamber 10. Auxiliary pump 50 is used to produce a low level of vacuum within the reaction chamber 10 via the second pipe 40. The scrubber 70 collects and refines air or reaction gas discharged through a third pipe 60 connected to the auxiliary pump 50, and then discharges the refined air or reaction gas.
Reaction gases used in the manufacturing process are supplied into the reaction chamber 10 through an external reaction gas supply section (not shown). Also, plasma may be produced from the reaction gases to enhance the efficiency and uniformity of the process. To this end, various types of electrodes may be used to excite the reaction gases. Furthermore, a susceptor or an electrostatic chuck may be provided at a lower portion of the reaction chamber 10 to support the wafer. The apparatus may also employ sensors to detect various states of the process occurring in reaction chamber 10. Typically, these sensors are incorporated into a sidewall of the reaction chamber 10 or are disposed in upper and lower portions of the reaction chamber 10.
Also, a plurality of ports can be provided in the sidewall or in upper and lower walls of the reaction chamber 10. The ports define passages open to the inside of the reaction chamber 10. Preferably, the first and second pipes 30 and 40 are connected to the ports.
In one form of conventional semiconductor device manufacturing equipment, a plurality of the reaction chambers 10 are clustered and connected to each other. In this case, the second pipe 40 is connected to one of the reaction chambers 10 of the cluster. Moreover, the main pump 20 directly cooperates with a port in the reaction chamber 10, i.e., is not connected to the reaction chamber 10 using a separate pipe, to maximize the efficiency by which the reaction chamber 10 can be evacuated. In general, a high performance turbo pump is used as the main pump 20 to produce a high level of vacuum in the reaction chamber 10. Such a turbo pump is disclosed in U.S. Pat. No. 4,036,565.
During an etching or deposition process, the conventional turbo pump pumps air or reaction gas from the reaction chamber 10 using a high speed rotor. However, as wafers having larger and larger diameters are used to manufacture semiconductor devices, larger reaction chambers must be used to accommodate such wafers. Thus, it takes a longer time to get the rotor up to speed to produce the high level of vacuum required in the reaction chamber.
The conventional turbo pump has the following disadvantages.
First, the speed of the turbo pump rotor must be gradually reduced during preventive maintenance (PM) of the reaction chamber 10 when the reaction chamber 10 is opened. In this respect, the turbo pump is shut down and the rotor is allowed to slow down on its own. Accordingly, it takes a relatively longer amount of time to reduce the speed of the rotor, which time results in lost productivity.
Second, the foreline valve 90 must be closed, and the turbo pump rotor must be stopped when a wafer is unloaded from the reaction chamber 10. However, if there is a leak in the foreline valve 90, the rotor may contact an adjacent stator and break. This can allow air back into the reaction chamber, which may contaminate the wafer and thus lower the manufacturing yield.